Deuteronomy 7:2–4

2 and when the Lord your God delivers them over to you and you defeat them, you must completely destroye them. Make no treaty with them and show them no mercy.f 3 You must not intermarry with them, and you must not give your daughters to their sons or take their daughters for your sons,g 4 because they will turn your sons away from me to worship other gods.h Then the Lord’s anger will burn against you,i and he will swiftly destroy you.